The present invention relates to a high-pressure pump with improved hub.
It applies in particular to a high-pressure pump for supplying a motor vehicle internal combustion engine with fuel. In this case, the transferred liquid is fuel.
The state of the art already knows a high-pressure pump for pumping a first liquid, known as the transferred liquid, of the type comprising a main unit for pumping the transferred liquid, which unit is actuated by a secondary unit for pumping a second liquid, known as the working liquid, the secondary unit comprising a hub mounted so as to rotate in a housing forming a bearing, and at least one piston for compressing the working liquid, which can move approximately parallel to the axis of rotation of the hub, returned elastically against a swashplate for actuating this piston, carried by the hub.
A pump of this type is described for example in WO 97/47883.
The hub of the pump described in the above document is mounted so as to rotate in the housing by means of ball bearings which rotationally guide and axially position the hub in the housing. These ball bearings have the drawbacks of being bulky, relatively heavy and expensive and sometimes sources of noise.
It is an object of the invention to propose a high-pressure pump of the aforementioned type having means for rotationally guiding and axially positioning the hub in the housing which are effective, simple and compact.
To this end, the subject of the invention is a high-pressure pump of the aforementioned type, characterized in that the hub comprises a peripheral cylindrical surface for guiding the rotation in the housing, extended by a shoulder for axially positioning the hub in the housing, the peripheral guide surface and the axial positioning shoulder cooperating respectively with complementary rotational guiding means and complementary axial positioning means carried by the housing, the axial positioning shoulder being urged against the complementary axial positioning means carried by the housing and by the elastic return force of the piston and the pressure of the working liquid in contact with the swashplate.
According to other features of this pump:
the peripheral guide surface is formed by the external surface of a sleeve, the axial positioning shoulder being formed by one face of a ring attached to this sleeve;
the peripheral guide surface and the axial positioning shoulder are formed by the external surface of a stepped tubular member made as a single piece;
the peripheral guide surface is formed by the external surface of a sleeve, the axial positioning shoulder being delimited by a collar extending one end of this sleeve;
the complementary rotational guiding means comprise a cylindrical bearing surface in sliding contact with the peripheral guide surface for the hub and the complementary axial positioning means comprise a flat bearing surface in sliding contact with the shoulder;
the cylindrical bearing surface is formed by the internal surface of a liner of the housing, the flat bearing surface being formed by a washer arranged at one end of the liner;
the cylindrical bearing surface is formed by the internal surface of a sleeve, the flat bearing surface being delimited by a collar extending one end of the sleeve;
the complementary rotational guiding means comprise rolling bearing needles, carried by the housing running more or less parallel to the axis of rotation of the hub, and the complementary axial positioning means comprise rolling bearing needles, carried by the housing, running more or less radially with respect to the axis of rotation of the hub; and
the transferred liquid is a fuel for a motor vehicle internal combustion engine.